Determination of dynamic parameters of a structure such as predominant frequency and damping ratio is one of the most important subjects in dynamics of structures. Different methods are used to determine predominant frequency. These methods are different in the cost, implement accessibility, accuracy, speed, applicability in different conditions, simplicity of calculations and required data accessibility. Calculation of damping ratio by using common experimental procedures is very difficult and costly, then it is assumed as a constant value in most calculations. Microtremor measurements and using spectral ratio method to determine the predominant frequency and damping ratio of structure is of interest in recent years. In this paper, as a case study, the effects of retrofitting on structural dynamic parameters of two four-story buildings by using microtremor measurements and also finite element analysis, is investigated.
The results of this study show that microtremor measurements can be utilized to assess the improvement of
dynamic behavior of the retrofitted structure and the effectiveness of the method of retrofitting.